Russian Twists

From a sitting position on the floor, have your heels on the floor and knees bent. With your core engaged, lean back to a 45-degree angle. Hold your hands behind your head, and with elbows wide apart, start twisting slowly from left to right.

For a challenge, hold your hands above your head with palms together. Lower your hands to tap the ground on one side, then bring your hands back above your head; lower and tap the ground on the opposite side.